Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$162.46	8.442%	$176.1749	$176.17	$176.15	$176.20
Purchase #2	$24.52	3.289%	$25.3265	$25.33	$25.35	$25.30
Purchase #3	$79.81	12.194%	$89.542	$89.54	$89.55	$89.50
Purchase #4	$242.31	9.233%	$264.6825	$264.68	$264.70	$264.70
Purchase #5	$137.70	12.842%	$155.3834	$155.38	$155.40	$155.40
Purchase #6	$193.45	11.380%	$215.4646	$215.46	$215.45	$215.50
Purchase #7	$99.40	10.510%	$109.8469	$109.85	$109.85	$109.80
7 purchase totals =	$939.65		$1,036.4208	$1,036.41	$1,036.45	$1,036.40